Centrifugal unshorting device



Jan. 4,' 1949. L. R. HAFSTAD ETAL 0 CENTRIFUGAL UNSHORTING DEVICE Filed Jan. 27, 1943 FIG. 2

INVENTORS R. l/AFSTAD BY W/L F Err MILL/V? TTO Patented Jan. 4, 1949 CENTRIFUGAL UNSHORTING DEVICE Lawrence R. Hafstad and William J. Flett, Washington, D. 0., assignors to the United States of America as represented by the Secretary of the Navy Application January 27, 1943, Serial No. 473,762

3 Claims. 1

This invention relates to switches and more particularly to a so-called unshorting switch of novel construction which is adapted normally to shortcircuit an electrical element and is operable to remove the shortcircuit automatically in response to the dual action of a force of setback and centrifugal force. The new switch is of simple construction adapted for manufacture at low cost and is positive in operation. The invention may be employed to particular advantage in explosive projectiles of the type which rotates at high speed when fired from a gun, and, therefore the invention will be described in a form suitable for this use, although it will be understood that the invention may be used for other purposes as well.

One object of the invention resides in the provision of a novel unshorting switch for use in explosive projectiles, which remains unoperative except when subjected to both setback and centrifugal forces. A switch made in accordance with the invention comprises a shortcircuiting element, preferably in the form of a wire extending between a pair of terminals, and means operable by centrifugal force to rupture the shortcircuiting element. The rupturing means is normally secured against movement by a stop operable by a force of setback to release the rupturing means.

Another object of the invention is to provide an unshorting switch for use in electrical fuzes for projectiles, which is simple, compact, positive in action and capable of withstanding the usual drop and tumble tests for fuzes.

These and other objects of the invention may be better understood by reference to the accompanying drawing, in which Fig. 1 is a perspective view of one form of the new switch, with parts broken away;

Fig. 2 is a plan view of the switch shown in Fig. 1;

Fig, 3 is a sectional view on the line 3-3 in Fig. 2, and I Fig. 4 is a schematic view of the switch, showing the wiring for connecting it in a fuze detonating circuit.

Referring to the drawing, the switch there shown comprises a cylindrical body I made of a suitable insulating material, such as Lucite, and having in its rear face a recess I I for receiving a detonating squib, to be referred to in greater detail presently. In its front face, the body is provided with a generally circular groove or rout I2 lying inwardly from the edge of the body and substantially concentric to the axis thereof, the

groove being circular except for a straight portion I2a. A passage. I3 parallel to the straight groove portion I'2a connects the recess II to the curved part of the groove. At the ends of the straight groove portion I2a are recesses I5 and I6 containing terminals I1 and I8 respectively secured to the switch body. A radial passage 20 extends inwardly from the edge of the body to the groove I 2a between the recesses I5 and I6 and receives a centrifugally operated element in the form of a plunger 2| which fits losely in the passage. A shortcircuiting wire 22 in the groove I2a is connected at its ends to the terminals I! and I8 and extends through an opening in the inner end of the plunger, which normally projects into the groove.

A plu 24 threaded into the rear face of the switch body has a bore 25 terminating short of the rear end of the plug and communicating at its front end with the radial passage2l! through an aligned opening in the switch body, The bore 25 contains a detent 26 projecting through the aligned opening into a recess :21 in'the'plunger, the detent having a shoulder 26a engaging a corresponding shoulder on the switch bodytolimit movement of the detent into the plunger. 1 A coiled sprin 28 seated on the closed end of the plug engages the detent 26 and urges it forwardly to maintain the detent in the plunger recess.

In the use of the new switch, a detonating squib 30 (Fig. 4) is placed in the recess I I and connected by wires 3| and 32 to the terminals I 1 and I8, respectively, the wires extending from the squib through passage I3 into the groove I2. It will be understood that the wire 3| extends from passage l3 counterclockwise (Fig. 2) along the groove I2 toterminal I'I, while'the wire32 extends clockwise in the groove from passage I3 to the terminal i 8. The terminals I1 and I8, in turn, are connected across a current source 33 in the projectile (not shown) through a circuit control device 34, such as a timin mechanism or a device responsive to proximity of a target to the projectile. The switch body I0, being cylindrical, is adapted to fit in the casing of the projectile with the groove I2 facing the nose of 'the pro-- whereby accidental breaking of the shortcircuiting wire 22 is prevented. However, when the projectile is fired in a gun, the resulting force of setback causes the detent 26 to move rearwardly out of the plunger recess 21 against the action of sprin 28. Accordingly, the plunger is released and-"the centrifugal foncerincident' to rotation of the projectile by the riding in the gun causes the plunger to move outwardly in the passage 20 and break the shortcircuiting wire 22. The retonating squib 30 is then unshorted so that the fuze is armed and made ready for firing by the control device 34.

The switch of our invention may be -made in a compact form and provides'an elective safety means for preventing premature detonation of a projectile fuze. Since theplunger Ql-can move only in a direction normal to the axes of the switch body I!) and the projectile, it cannotbe actuated by the force of' setback. Also, since the detent 16 can move \oniyin adirection'parall'el to ;the 85201; the switchibodyand etherprojectile, it ,canenoti beractuateds by .centrifugalforce. nd -ccordingly-,- removaltof .theshortcircuit of 'the'detaonatingssquib requires the operation of thetwo interconnected elements ll 26 by :the i action of 'tworlnchependentrforces. lit will; be apparent'that arvith the new: iconstrmtiomlthe squib" 3U vcan not 'bemecidentallyjrmedi by idropping or tumbling 1the:pro tcetfle;.=heca,use .the:- pioneer: 2 I: for breakling:the tshiortcircuitrlng wire 22 is held positively sins-1n unarmed position by .the detent 2B,:which rmlmaeszthe ninngenmnly. in response-ton relaztively, Ingm mridircctional force, of setback incidentfioflflnmthe moiectile.

The dimensions of the operatingt-partsotthe with :may: be: Varied:v .to :suit-rpanticularcondiitions. I1;Howewer,'itlhas been foundithat-satisiac- :wryrtresultsrt-may be: obtained with: agplunger :welghing 0229 :pound, and as, shortwh'cuiting wirezhavingn rliameteri of r005inch, the plunger mfodzwinga shearupull, on the: wire ot.i6.4' pounds .with minimum aequiredurotation. of Ethe:pl0.lEC- tile mneoo :emlutione-lper rsecond at: annangul a1- second pnmseoond. tTheJweighhbf ithe detent" -26 ithedmmiierti:inv lthe spring :28 shouldzbe .careimliyapmthminedntoi balance the aweight of plunger: ll urdrhmireithatthepiunger is released by the wheat-only when thedevice. issubiected to a'rforceof setback :01 theldesined -magnitude.

-wmlerwezhare shown the. locking detent; 26

body 2| 0, .the plunrmay be eliminated :byxmounting lthaidetentzaand snringydirectlysin abore-fin ithe body. 'dlhe, boreamay; be! formed. tor-extend zfrom the h'onttacemfsbody ll and-terminateshortof the-wear :tace; so that; ,the bore ;-interaects; passage '20 and :the. springhos anse'aton ithegclosedrear end 'ofthebore. Thusnin assemblingrthedevice, the, detent. maypbe': hclcbrctracted 'inxthe Y bore against spring :28 :by, a wirepinserted through the front end-of the boraxmntil the; plunger, 2| -is moved inwardly toa positionv overlying partof :the

detent,- wherewonthewire may be removed: and

the plunger shifted-to its v-innermost position so that the detent snaps into recess 21. This:.constr-uction --is .well adapted :forlarge scale production, and may: be preferred to that illustrated in Figs; 1 to 3,,inchisi-ve.

body for locking the rupturing means in an inoperative position and movable by a force of setback to release the rupturing means.

2."An unshorting switch for use in a rotating projectile, which comprises an insulating body having a squib-receiving recess in one end of the i body'and. a groove'in the other end of the body 'wire, theplunger being movable radially of the axisoft-he'body by centrifugal force to break the "wire, and means in the body for locking the plunger-in an inoperative position and movable by force of'setback to release the plunger.

3. An unshorting switch for use in a rotating projectila-Which comprises et -generally cy ndrical insulating body havinga squih-receiv lg: recess in one end and a gI'OOVein the oppcsiteend, the groove extending in a closed path having a "straight portion, terminals mounted in the groove at "the endsofthe straight portion thereof, the body having a passage connecting said recess with the'groove, andthe passage and groove forming a means for conducting xvi-ring from the re ess ":0 said terminals, a s'hortcircuiting wire disposed in the straight portion of the groove and connected between the terminals. a plunger in the body projecting into the groove and "connected to the 'shortcircuiting wirepthe' plunger being movable ra'diallyinthe' body to break the wire inresponse to centrifugal force, a detent inthe body projecting'into the plunger for locking the plungerin arr-inoperative position, and a spring normally urging the detent into theplunger, the detent being movable in the bodyagainst the spring by a forced setback to releasethe plunger.

LAWRENCE R HAFSTAD. WILLIAM J. FLETT.

REFERENCES ClTED ,The following references are of record in the file of this patent:

STATESPATENTS Number Name Date 571,909 'Scribner Nov, 24, 1896 1,806,877 Hale May 26, 1931 FOREIGN PATENTS Number Country Date 6,757 Great Britain Mar. 19, 1912 91,592 Sweden Feb. 24, 1938 376,987 Italy Dec. 4, 1939 668,368 Germany "Dec. 1, 1938 

